As an experienced sommelier and brewer, I can confidently say that the flavor of beer can degrade over time. This is particularly true when it is exposed to light, oxygen, and heat, which can all have a negative impact on the organic compounds that contribute to the wonderful smell and taste of beer. However, it is important to note that even when the flavor of beer is declining, it can still be perfectly safe to drink.
When beer is canned, it is typically done so under controlled conditions to ensure its freshness and quality. Cans provide a great barrier against light and oxygen, which helps to protect the beer from degradation. However, over time, even with the best packaging, some changes can occur.
One of the primary factors that can affect the flavor of beer over time is oxidation. Oxygen can slowly seep into the can, causing chemical reactions that can alter the taste and aroma of the beer. This can result in off-flavors such as a papery or cardboard-like taste. Additionally, the hops in the beer, which contribute to its bitterness and aroma, can break down and lose their potency over time, leading to a less vibrant and fresh taste.
Another factor to consider is the impact of heat. Beer is best stored at cool temperatures, as heat can accelerate the aging process and cause the beer to spoil more quickly. If the beer has been exposed to prolonged periods of high temperatures, it is more likely to have undergone significant flavor changes.
That being said, it is important to remember that beer doesn't necessarily become unsafe to consume as it ages. The degradation of flavor does not necessarily mean that the beer has gone bad or is harmful. It simply means that the taste may not be as enjoyable as when it was fresh.
In my personal experience, I have come across beers that have been aged for several years and still maintained a decent level of drinkability. While the flavors may have mellowed and changed, they still offered an interesting and enjoyable drinking experience. However, I have also encountered beers that have not aged well and were undrinkable due to off-flavors and a complete loss of quality.
To summarize, while a 2-year-old canned beer may not taste as good as when it was fresh, it is important to note that it can still be safe to drink. The flavor degradation is a natural process that occurs over time, particularly when the beer is exposed to light, oxygen, and heat. It is always best to use your senses and judgment when evaluating the quality of aged beer, and if in doubt, it's better to err on the side of caution and opt for a fresher option.